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It is generally agreed that making real-world connections in mathematics teaching increases students' motivation and interest and contributes to meaningful and permanent learning. In this paper we propose a simple and fast activity to find a rectangular hyperbola in real life and we show how to operate the data to retrieve a straight line. Since it deals with simple formulas, we believe that it can be useful in a high-school context, either in math or physics class. The activity consists of assembling a wedge with transparent plates (like glass photo frames), dipping it on a liquid and observing the rise of a hyperbola. Instructions are given on how to obtain the coordinates of the liquid/air interface and how to replot them as a straight line, using just a smartphone. For the physics class, an extension is proposed to measure the surface tension of the chosen liquid.

This paper describes an experiment with two touching rotating disks, whose movement is followed by video analysis. Within the disks' movements, there are intervals with sliding and intervals without sliding, that is, intervals with frictional forces between the touching surfaces and intervals without it. This system configuration allows for measurement of the changeable magnitudes and directions of frictional forces (much more difficult to set up with translational motion). This activity may be used to combat students' misconceptions of "frictional force always opposes the motion" and "between the same two bodies, one gets the same frictional force," commonly found in the classroom, or just to reinforce the rotational dynamics relationships.

This paper describes a conservation of momentum experiment using just smartphones and two beach balls, thus making the experimental study of this movement available to any classroom. For a more thorough analysis of the data, a computer can also be used. Experiments making use of smartphone sensors have been described before, contributing to an improved teaching of classical mechanics. In this experiment, we have made use of two smartphone cameras together with the VidAnalysis free app to track the position of two balls colliding in air during a projectile motion (Fig. 1).